1. Field of Invention
The present invention relates to power-assisted bicycles, and more particularly to an electric power-assisted bicycle having multiple magnetic induction points arranged on a rotary element to provide power assistance signal.
2. Description of Related Arts
As disclosed in the Chinese patent application Claw-type Moment Sensing Device, CN201020295192.0, by CHINA YEBAO BICYCLES INC. (KUNSHAN) CO., LTD, the sensing device for the power-assisted bicycles comprises the magnetic element and the elastic element cooperating with the magnetic element, so as to sense the moment. After a long-time service, the change in the elasticity coefficient of the elastic element leads to the change in the control effects between the sensing signal and the controlled motor; the power assistance effect becomes mis-matched with the user power assistance demand. The complicated structure of the elastic element raises the manufacture cost.
As disclosed in the Chinese patent Automatic Detection Device for Electric Power-assisted Bicycle, with the application number of CN01201843.0, by UNIVERSITY OF SCIENCE AND TECHNOLOGY BEIJING, the automatic detection device for the electric power-assisted bicycles is capable of detecting the pedal force, the speed and the steering direction without contact. In the automatic detection device, the magnetic sheets are respectively provided on the inner wheel and the outer wheel in the relative motion. The spring is provided on the inner wheel. The inner and the outer wheels are recovered via the spring. The two Hall components are provided on the rack to induce the relatively moving magnetic sheets on the inner and the outer wheels, and thereby the electric signals are generated to indicate the pedal force, the speed and the steering direction.
Firstly, the elastic element has a poor durability. After a long-time service, the elasticity coefficient of the elastic element changes, so that the control effects between the sensing signal and the controlled motor also changes. As a result, the power assistance effect becomes mis-matched with the user power assistance demand. The complicated structure of the elastic element raises the manufacture cost.
Secondly, each group of the magnetic sheets is identical with each other and has the same magnetic poles arrangement, so as to fail to represent respective positions of the different groups of the magnetic sheets and be disenabled to express special power assistance demand at different positions. As disclosed in FIGS. 3, 4, 5 and 6 and paragraph 2 on page 2 of the specification in the Chinese patent with the application number of CN01201843.0, each group of the magnetic sheets, comprising a first magnetic sheet 4, a second magnetic sheet 5 and a third magnetic sheet 6, has the same magnetic poles arrangement; in other words, the identical groups of the magnetic sheets are merely repeatedly provided at different positions of the inner wheel, thereby failing to represent the respective positions of the different groups of the magnetic sheets and to express a motion state at a specific position. When the user is riding on the bicycle, the pedal and the motion state of the pedal at the corresponding position have the correspondingly special power assistance demand. However, the Chinese patent with the application number of CN01201843.0, fails to express the special power assistant demand of the pedal at the respective position due to the identical structure of each group of the magnetic sheets.
Thirdly, the signals at different induction points have no difference, causing the man-machine mis-match. Each group of the magnetic sheets is identical, so that each group is unable to represent the position of the group at the inner wheel. The signal outputted by the Hall component is unable to represent the positions of the pedal and other groups of the magnetic sheets, namely the signal outputted by the Hall component is unable to represent the power assistant demand at different positions of the pedal, which results in the mis-match between the power assistance demand and the time of supplying power assistance, i.e., the unsatisfactory man-machine cooperation.
Fourthly, the outputted sine wave restricts the distance between the edge of each group of the magnetic sheets to be no smaller than 4 cm, preferably 5 cm, in such a manner that the permitted number of the groups of the magnetic sheets is too small, also causing the unsatisfactory man-machine cooperation. Each group of the magnetic sheets is identical, and the sine wave is outputted by the Hall component as the control signal. The sine wave as the control signal requires a certain difference between peak and valley. Since the groups of the magnetic sheets need a certain length to represent the forward motion and the backward motion, at most 8 groups, preferably 5 groups, are provided at the circular track of the rotary disc with the ring-shaped groove and the diameter of 20 cm so that the Hall component generates the sine wave signal with the control function. In other words, according to the Chinese patent with the application number of CN01201843.0 for the power-assisted bicycles, the number of the groups is restricted within 8, which results in too few control signals and the unsatisfactory man-machine cooperation. If more than 8 groups of the magnetic sheets are provided, the signal outputted by the Hall component would become almost a horizontal line when the bicycle is running fast, wherein the signal is without the control function and unable to control the motor, which means that the motor is disenabled to provide power assistance when the bicycle particularly needs the power assistance.
Fifthly, the signal blind zone reaches 45°, and the demand for the power assistance when launching the bicycle may be unsatisfied. As is known to all, the moment of the pedal stepped by the man at the top is the smallest, and the range of 10°-45° away from the top is the zone where the power assistance is most necessary. However, in the Chinese patent with the application number of CN01201843.0, the angle between each group of the magnetic sheets is 45°; within the range of 10°-45° away from the top, there is no group of the magnetic sheets, and thus no control signal is generated, which results in that the motor is unable to provide power assistance when the bicycle needs the power assistance the most.
Therefore, besides the poor durability and the complicated structure of the elastic element, the number of the groups of the magnetic sheets is restricted within 8 when the wheel has the diameter of no more than 20 cm, due to the structural cooperation between the Hall component and the magnetic sheets. With the number of the groups of the magnetic sheets strictly controlled, the man-machine cooperation is unsatisfactory; the motor is unable to assist the launch of the bicycle, and the demand for the power assistance is mis-matched with the supply of the power assistance, which results in the poor comfort for the bicycle riders. If the number of the groups of the magnetic sheets is added forcibly, the sensing signal loses the control function over the power assistance.
As disclosed in the Chinese patent with the application number of CN03264387.X by Wang Naikang, titled Timing Sensor for Electric Power-assisted Bicycle, no elastic element is involved; only the movable wheel and the static wheel are provided. The movable wheel is embedded with the two permanent magnets; the static wheel is embedded with the three Hall components. When the pedal rotates one circle, each Hall component generates two pulses, and the three Hall components generate six pulses. The features and the defects thereof are as follows.
Feature (1): in order to obtain the six pulse signals, the same magnetic poles of the permanent magnets are provided at the same side. Each Hall component is intended to generate two pulses, and thus the same magnetic poles of the two permanent magnets are provided at the same side of the movable wheel, namely either two north poles or two south poles of the two permanent magnets are provided at the side of the movable wheel. If a north pole and a south pole respectively of the two permanent magnets are provided at the same side of the movable wheel, when the pedal rotates one circle, each Hall component would generate one pulse, and the three Hall components would generate three pulses, which is different from the disclosure of the Chinese patent with the application number of CN03264387.X. In order to increase the number of the pulses and improve the control effect, the same magnetic poles of the permanent magnets have to be at the same side.
Feature (2): the permanent magnets represent fixed positions of the pedals, and the three Hall components represent motion positions of the pedals. The pedals and the rotary wheel rotate synchronously, so each permanent magnet is respectively mounted at the two positions on the rotary wheel corresponding to the two pedals. Whatever position the pedal is rotated to, the corresponding permanent magnet is rotating to the same position. However, merely by rotating the pedals to the positions where the Hall components are located, the control signal is sent out via the Hall components to instruct the motor of the power-assisted bicycle to generate the demanded power assistance.
Feature (3): since one Hall component is unable to represent the different motion positions of the pedal at the different time in one circle of rotating, merely one Hall component is insufficient. At the different time in one circle of rotating, the pedal has different demand for power assistance. In order to indicate the change in the demand for power assistance, according to the disclosure in the Chinese patent with the application number of CN03264387.X, the three Hall components are respectively provided at the three positions within 180°, wherein two Hall components thereof are mounted at the positions of the two pedals. Once the pedals rotate to the positions where the Hall components are located, the Hall components output the signals, which represents that the pedals are at the positions of the Hall components. Nevertheless, the multiple Hall components have the following defects.
The sensor for the power-assisted bicycle has the following five defects.
Defect (1): the fixed positions of the two pedals are respectively represented by the two identical permanent magnets, and thus the multiple Hall components are required to represent the motion positions of the two pedals. The two permanent magnets are identical so that the fixed positions of the two pedals are represented without distinguishing the left pedal and the right pedal, in such a manner that the left pedal and the right pedal are provided with identical power assistance together. However, the permanent magnets per se are still unable to represent the motion positions of the two pedals; the motion positions of the two pedals have to be represented by the several Hall components which are provided at different angular positions. Therefore, merely one Hall component is insufficient, and the multiple Hall components are necessary.
Defect (2): only one Hall component is insufficient, but the three Hall components certainly results in the original segmental error among the three control signals, which means that the power assistance demand model distorts and the power assistance output is naturally mis-matched with the power assistance demand. No matter the power-assisted bicycle has one motor or two motors, the motor is only under the control of one sensing signal which is inputted into the motor controller. In the Chinese patent with the application number of CN03264387.X, the three Hall components are for controlling the motor, so the three control signals of the three Hall components must be combined into a combined control signal before being inputted into the motor controller. The three Hall components have different sensing parameters. Especially because of the changed environmental temperature and the long-time service, there may be a great difference among the sensing parameters of the three Hall components. As a result, in accordance to the identical power assistance demand, each Hall component output different voltages, leading to different power assistance outputs of the motor. The power assistant outputs become mis-matched with the power assistance demand. Similarly, in accordance to respectively different power assistance demands, each Hall component may output identical voltages, leading to identical power assistance outputs of the motor. The power assistance outputs also become mis-matched with the power assistance demands.
Defect (3): combining the control signals is liable to generate the signal drift so that the combined control signal is mis-matched with the motor controller and the power assistance demand model distorts. Because of the change in the environmental temperature and the long-time service, there may be a great difference among the sensing parameters of the three Hall components; the connection points of the three control signals of the three Hall components certainly changes; and thus, the combined control signal generated by the identical power assistance demand generates the segmental signal drift. The combined control signal, as a whole, generates the signal distortion, namely the power assistance demand model distortion. As a result, no matter which one of the three control signals is chosen by the motor controller as the reference, the power assistance output is always mis-matched with the power assistance demand.
Defect (4): it is forbidden to arbitrarily add the number of the induction points; with the small number of the induction points, the motor operates unstably, which brings discomfort to the bicycle rider. The defects (1) and (2) are caused by the more than one Hall components. Obviously, the defects (1) and (2) would deteriorate by increasing the number of the Hall components. Therefore, the power-assisted bicycle according to the Chinese patent with the application number of CN03264387.X is always uncomfortable for the bicycle rider.
Defect (5): the signal blind zone reaches 42°, and the demand for the power assistance when launching the bicycle is unsatisfied. As is known to all, the moment of the pedal at the top is the smallest, and the range of 10°-45° away from the top is the zone where the power assistance is most necessary. However, in the Chinese patent with the application number of CN03264387.X, the angle between each Hall component is 42.5°-43.5°; within the range of 10°-42° away from the top, there is no Hall component, and thus no control signal is generated, which results in that the motor is unable to provide power assistance when the bicycle needs the power assistance the most.
As a conclusion, according to the Chinese patent with the application number of CN03264387.X, the multiple Hall components are used to control the power assistance, since the multiple Hall components are necessary for representing the motion positions of the pedals. However, the multiple control signals of the multiple Hall components certainly have the original error, while the combined control signal is liable to generate the signal drift, which distorts the power assistance demand model. In other words, the identical power assistance demand at different time is supplied with different power assistance. On one hand, the more Hall components, the more the power assistance demand model distorts. On the other hand, if the number of the Hall components is restricted, the small number of the Hall components results in the unstable operation of the motor, the big discomfort for the bicycle rider and the launch in lack of power assistance. It is mutually contradictory and incompatible to protect the power assistance demand model from distortion and to ensure the stable operation of the motor.